Diplo is the DJ who performs at Sebastian's Pokémon arena in Pokémon Detective Pikachu. He appears as himself, credited in the film simply as the DJ at the underground battle venue.
The arena sequence takes place in Ryme City, where Tim Goodman and Pikachu investigate clues connected to Tim's missing father, Harry Goodman. Sebastian is a Pokémon trainer who challenges Pikachu to a battle against his Charizard. The loud music, crowd, and underground atmosphere establish the arena as one of the film's most distinctive settings.
Diplo is the stage name of Thomas Wesley Pentz, an American DJ, producer, and songwriter. He is known for solo work and for projects including Major Lazer and LSD. His brief appearance is a cameo rather than a major acting role, so viewers may remember the music and setting without recognizing him immediately.
The scene is also easy to confuse with the original Detective Pikachu video game, but the 2019 film changes and expands many story details, including the arena sequence and Diplo's cameo.